(a) Field of the Invention
The present invention relates to a method of preparing a polyamide, and particularly to an economical method of preparing a heat-resistant polyamide in that a monomer, a raw material, is simply and chiefly prepared and the polymerizing reaction time is short because it does not need a solvent separately.
(b) Description of the Related Art
A polyamide represented by nylon 6 and nylon 66 is widely used to fibers, films, sheets, injection-molded articles, and the like because of its superior mechanical properties and chemical resistance. However, there is a problem of that the heat-resistance of nylon 6 and nylon 66 is insufficient to be applied to semiconductor processing equipments, circuit boards, parts of automobiles and airplanes, and the like, because they have the melting temperature of 230° C. and 260° C., respectively, and thus do not have sufficient heat resistance.
To resolve the problem related to the heat-resistance, nylon 46 was prepared by reacting butane diamine and adipic acid, and it has relatively high melting temperature of 290° C. However, it has a limit to its application due to hygroscopic property due to high amide bonds density, and it also has a limit to be widely used because the monomers of the aromatic polyamide obtained by using an aromatic dicarboxylic acid and an aromatic diamine instead of an aliphatic dicarboxylic acid or an aliphatic diamine are expensive.
In addition, there are high heat-resistant resin such as a polyimide, a polyetherketone, an aromatic polyamide, a polyphenylenesulfide, and the like. However, they have disadvantages of that they are also expensive and their preparing methods are complicated.
That is, prior methods of preparing the polyamide are carried out by preparing a salt of dicarboxylic acid and diamine in diethanol, separating the salt therefrom, dissolving the separated salt into plenty of solvent, for example plenty of water, eliminating the water with pressured and vacuum condition at high temperature, and so on, and thus the methods are complicated. Furthermore, the methods are not economical because the methods consume plenty of water and need much energy to eliminate the water.